Techniques of guiding optical waves in planar optical materials, with an ultimate objective of achieving integrated optics similar to integrated electronics, have been advancing rapidly in the last few years. Optical waveguide components such as modulators, deflectors, lasers, detectors and other passive and active devices are being demonstrated and developed in research laboratories throughout the world. The activity can be divided into the following areas: (1) the development of techniques of guiding the optical waves, (2) the development of suitable materials media and (3) the development of modern microfabrication technology. It is of paramount importance to the objective of optical integration that all of these can be simultaneously satisfied in a material which possesses desirable physical effects.
Waveguiding in many useful optical media has been achieved. Thin film waveguides have been prepared on suitable substrates by, for example, sputtering, R. H. Deitch, E. J. West, T. G. Giallorenzi and J. F. Weller, "Sputtered Thin Films for Integrated Optics", Appl. Opt., 13, 712 (1974) and epitaxial growth, W. T. Lindley, R. J. Phelan, C. M. Wolfe and A. G. Foyt, Appl. Phys. Lett., 14, 197 (1969). Waveguiding has also been achieved by modification of the refractive index of the medium surface by diffusion, I. P. Kaminow and J. R. Carruthers, Appl. Phys. Lett., 22, 326 (1973); proton irradiation, E. R. Schineller, R. P. Flan and D. W. Wilmot, "Optical Waveguides Formed by Proton Irradiation of Fused Silica", J. Opt. Soc. Am., 58, 1171 (1968); and ion implantation, E. Garmire, H. Stoll, A. Yariv and R. G. Hunsperger, Appl. Phys. Lett., 21, 87 (1972).